The present invention relates to improvements in apparatus which serve to compensate for fluctuations of torque between the engine and the transmission of a motor vehicle. More particularly, the invention relates to improvements in apparatus which can be utilized between the crankshaft of an internal combustion engine and the input shaft of a change-speed transmission in an automotive vehicle to reduce shocks which develop when the magnitude of torque which is transmitted by the crankshaft fluctuates within a wide or a narrow range. Still more particularly, the invention relates to improvements in apparatus wherein several dampers serve to transmit torque between a plurality of coaxial flywheels including a first flywheel which is driven by the crankshaft of the engine and a second flywheel which can drive the input shaft of the change-speed transmission and is rotatable relative to the first flywheel.
An apparatus of the just outlined type is disclosed, for example, in U.S. Pat. No. 4,274,524 to Nakane. The apparatus of Nakane comprises a slip clutch and an elastic damper which is in series with the slip clutch and comprises a set of energy storing elements in the form of coil springs. The elastic damper of the patented apparatus further comprises a friction generating device which is mounted in parallel with the coil springs. The slip torque of the clutch considerably exceeds the maximum nominal torque which is generated by the internal combustion engine so that the clutch ceases to transmit torque only when the magnitude of transmitted torque fluctuates within a rather wide range.
The patented apparatus can bring about a reduction of stresses upon the power train between the engine and the wheels of a motor vehicle so that it reduces the likelihood of generation of excessive noise and contributes, to a certain degree, to the comfort of the occupant or occupant of the vehicle. However, the patented apparatus also exhibits certain serious drawbacks, particularly because it cannot ensure a predictable compensation for fluctuations of torque within the entire RPM range of the internal combustion engine. One of the reasons for such failure of the patented apparatus to operate properly within the entire RPM range is that the slip clutch responds only to very pronounced fluctuations of torque above the nominal torque which is transmitted by the internal combustion engine. The slip clutch of the patented apparatus transmits a maximum torque also when the engine operates within the lower part of the RPM range so that the apparatus cannot compensate for relatively small fluctuations of torque which is transmitted by the engine. This affects the comfort of the occupant or occupants and contributes significantly to the generation of noise during the aforementioned stages of operation of the engine.